package cn.diancan.util;

public class SecBase64 {
	private static final byte[] encodingTable = { (byte) 'A', (byte) 'B',
	    (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
	    (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L',
	    (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q',
	    (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V',
	    (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a',
	    (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f',
	    (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k',
	    (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p',
	    (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
	    (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
	    (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4',
	    (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9',
	    (byte) '+', (byte) '/' };
	private static final byte[] decodingTable;
	static {
	   decodingTable = new byte[128];
	   for (int i = 0; i < 128; i++) {
	    decodingTable[i] = (byte) -1;
	   }
	   for (int i = 'A'; i <= 'Z'; i++) {
	    decodingTable[i] = (byte) (i - 'A');
	   }
	   for (int i = 'a'; i <= 'z'; i++) {
	    decodingTable[i] = (byte) (i - 'a' + 26);
	   }
	   for (int i = '0'; i <= '9'; i++) {
	    decodingTable[i] = (byte) (i - '0' + 52);
	   }
	   decodingTable['+'] = 62;
	   decodingTable['/'] = 63;
	}

	//加密
	public static byte[] encode(byte[] data) {
	   byte[] bytes;
	   int modulus = data.length % 3;
	   if (modulus == 0) {
	    bytes = new byte[(4 * data.length) / 3];
	   } else {
	    bytes = new byte[4 * ((data.length / 3) + 1)];
	   }
	   int dataLength = (data.length - modulus);
	   int a1;
	   int a2;
	   int a3;
	   for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
	    a1 = data[i] & 0xff;
	    a2 = data[i + 1] & 0xff;
	    a3 = data[i + 2] & 0xff;
	    bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
	    bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
	    bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
	    bytes[j + 3] = encodingTable[a3 & 0x3f];
	   }
	   int b1;
	   int b2;
	   int b3;
	   int d1;
	   int d2;
	   switch (modulus) {
	   case 0: 
	    break;
	   case 1:
	    d1 = data[data.length - 1] & 0xff;
	    b1 = (d1 >>> 2) & 0x3f;
	    b2 = (d1 << 4) & 0x3f;
	    bytes[bytes.length - 4] = encodingTable[b1];
	    bytes[bytes.length - 3] = encodingTable[b2];
	    bytes[bytes.length - 2] = (byte) '=';
	    bytes[bytes.length - 1] = (byte) '=';
	    break;
	   case 2:
	    d1 = data[data.length - 2] & 0xff;
	    d2 = data[data.length - 1] & 0xff;
	    b1 = (d1 >>> 2) & 0x3f;
	    b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
	    b3 = (d2 << 2) & 0x3f;
	    bytes[bytes.length - 4] = encodingTable[b1];
	    bytes[bytes.length - 3] = encodingTable[b2];
	    bytes[bytes.length - 2] = encodingTable[b3];
	    bytes[bytes.length - 1] = (byte) '=';
	    break;
	   }
	   return bytes;
	}

	//解密

	public static byte[] decode(byte[] data) {
	   byte[] bytes;
	   byte b1;
	   byte b2;
	   byte b3;
	   byte b4;
	   data = discardNonBase64Bytes(data);
	   if (data[data.length - 2] == '=') {
	    bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
	   } else if (data[data.length - 1] == '=') {
	    bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
	   } else {
	    bytes = new byte[((data.length / 4) * 3)];
	   }
	   for (int i = 0, j = 0; i < (data.length - 4); i += 4, j += 3) {
	    b1 = decodingTable[data[i]];
	    b2 = decodingTable[data[i + 1]];
	    b3 = decodingTable[data[i + 2]];
	    b4 = decodingTable[data[i + 3]];
	    bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
	    bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
	    bytes[j + 2] = (byte) ((b3 << 6) | b4);
	   }
	   if (data[data.length - 2] == '=') {
	    b1 = decodingTable[data[data.length - 4]];
	    b2 = decodingTable[data[data.length - 3]];
	    bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
	   } else if (data[data.length - 1] == '=') {
	    b1 = decodingTable[data[data.length - 4]];
	    b2 = decodingTable[data[data.length - 3]];
	    b3 = decodingTable[data[data.length - 2]];
	    bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
	    bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
	   } else {
	    b1 = decodingTable[data[data.length - 4]];
	    b2 = decodingTable[data[data.length - 3]];
	    b3 = decodingTable[data[data.length - 2]];
	    b4 = decodingTable[data[data.length - 1]];
	    bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
	    bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
	    bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
	   }
	   return bytes;
	}

	//解密

	public static byte[] decode(String data) {
	   byte[] bytes;
	   byte b1;
	   byte b2;
	   byte b3;
	   byte b4;
	   data = discardNonBase64Chars(data);
	   if (data.charAt(data.length() - 2) == '=') {
	    bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
	   } else if (data.charAt(data.length() - 1) == '=') {
	    bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
	   } else {
	    bytes = new byte[((data.length() / 4) * 3)];
	   }
	   for (int i = 0, j = 0; i < (data.length() - 4); i += 4, j += 3) {
	    b1 = decodingTable[data.charAt(i)];
	    b2 = decodingTable[data.charAt(i + 1)];
	    b3 = decodingTable[data.charAt(i + 2)];
	    b4 = decodingTable[data.charAt(i + 3)];
	    bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
	    bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
	    bytes[j + 2] = (byte) ((b3 << 6) | b4);
	   }
	   if (data.charAt(data.length() - 2) == '=') {
	    b1 = decodingTable[data.charAt(data.length() - 4)];
	    b2 = decodingTable[data.charAt(data.length() - 3)];
	    bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
	   } else if (data.charAt(data.length() - 1) == '=') {
	    b1 = decodingTable[data.charAt(data.length() - 4)];
	    b2 = decodingTable[data.charAt(data.length() - 3)];
	    b3 = decodingTable[data.charAt(data.length() - 2)];
	    bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
	    bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
	   } else {
	    b1 = decodingTable[data.charAt(data.length() - 4)];
	    b2 = decodingTable[data.charAt(data.length() - 3)];
	    b3 = decodingTable[data.charAt(data.length() - 2)];
	    b4 = decodingTable[data.charAt(data.length() - 1)];
	    bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
	    bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
	    bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
	   }
	   return bytes;
	}

	private static byte[] discardNonBase64Bytes(byte[] data) {
	   byte[] temp = new byte[data.length];
	   int bytesCopied = 0;
	   for (int i = 0; i < data.length; i++) {
	    if (isValidBase64Byte(data[i])) {
	     temp[bytesCopied++] = data[i];
	    }
	   }
	   byte[] newData = new byte[bytesCopied];
	   System.arraycopy(temp, 0, newData, 0, bytesCopied);
	   return newData;
	}

	private static String discardNonBase64Chars(String data) {
	   StringBuffer sb = new StringBuffer();
	   int length = data.length();
	   for (int i = 0; i < length; i++) {
	    if (isValidBase64Byte((byte) (data.charAt(i)))) {
	     sb.append(data.charAt(i));
	    }
	   }
	   return sb.toString();
	}

	private static boolean isValidBase64Byte(byte b) {
	   if (b == '=') {
	    return true;
	   } else if ((b < 0) || (b >= 128)) {
	    return false;
	   } else if (decodingTable[b] == -1) {
	    return false;
	   }
	   return true;
	}

	//测试类
	public static void main(String[] args) {
	   String data = "wizzer@qq.com:etpass";
	   byte[] result = SecBase64.encode(data.getBytes());// 加密
	   System.out.println("Basic "+data);
	   System.out.println("Basic "+new String(result));
	   System.out.println(new String(SecBase64.decode(new String(result))));// 解密
	   }
}
